The increase in isoprene concentration under normal conditions depends on sleep, and isoprene is believed to play a role in sleep regulation and to also be involved in sleep upholding.^1–3 Studies involving human subjects, where their breath samples were collected in 1 L Teflon bags through the use of gas chromatography and mass spectroscopy, have confirmed that healthy humans 15 to 60 years old who stay awake have an isoprene level of 14.6 ± 6.4 nmol/L (i.e., 8.2–21 nmol/L).¹

The molar mass of isoprene is 68.12g/mol, so the normal isoprene concentration in wakefulness corresponds to 509 ppb–1.43 ppm in adults. When asleep, adults’ isoprene levels rise to 3 ppm or more. Furthermore, “in the absence of sleep during the night, the concentration of isoprene in the breath did not increase.”¹